Role of perioperative dynamic sentinel node biopsy for cN0 penile cancer management: experience from an Italian tertiary referral center

New EAU/ASCO guideline recommendations on sentinel node biopsy for penile cancer and remaining challenges from a nuclear medicine perspective

INTRODUCTION

The European Association of Urology (EAU) and the American Society of Clinical Oncology (ASCO) recently issued updated guidelines on penile cancer, emphasising dynamic sentinel node biopsy (DSNB) as the preferred method for surgical staging among patients with invasive penile tumours and no palpable inguinal lymphadenopathy. This paper outlines the rationale behind this new recommendation and describes remaining challenges, as well as strategies for promoting DSNB worldwide.

MAIN TEXT

DSNB offers high diagnostic accuracy with the lowest postoperative complications compared to open or minimally invasive inguinal lymph node dissection (ILND), prompting its preference in the new guidelines. Nevertheless, despite its advantages, there are challenges hampering the widespread adoption of DSNB. This includes the false-negative rate associated with DSNB and the potential negative impact on patient outcome. To address this issue, improvements should be made in several areas, including refining the timing and interpretation of the lymphoscintigraphy and the single photon emission computed tomography/computed tomography images. In addition, the quantity of tracer employed and choice of the injection site for the radiopharmaceutical should be optimised. Finally, limiting the removal of nodes without tracer activity during surgery may help minimise complication rates.

CONCLUSION

Over the years, DSNB has evolved significantly, related to the dedicated efforts and innovations in nuclear medicine and subsequent clinical studies validating its efficacy. It is now strongly recommended for surgical staging among selected penile cancer patients. To optimise DSNB further, multidisciplinary collaborative research is required to improve SN identification for better diagnostic accuracy and fewer complications.

Accuracy of dynamic sentinel lymph node biopsy for inguinal lymph node staging in cN0 penile cancer

BACKGROUND

Penile cancer is characterized by an early lymphatic dissemination. In intermediate and high-risk primary tumors without palpable inguinal lymph nodes, there is a 6-30% risk of micro-metastatic disease. Invasive lymph node staging in these patients is performed using dynamic sentinel lymph node biopsy (DSNB). In this study, the role of DSNB in cN0 penile cancer was studied, evaluating features of sentinel lymph node (SN) visualization and outcome parameters. Patients with penile cancer without inguinal lymph node metastases who were referred for DSNB at our center between January 2015 and May 2021 and had a follow-up period of at least 18 months, were retrospectively included. After injection of 85 ± 20 MBq [^99mTc]Tc-nanocolloid peritumorally, dynamic, static planar and SPECT/CT imaging was performed. Primary endpoints were sensitivity of the diagnostic procedure, disease-free survival and DSNB-related adverse events. Secondary endpoints were SN detection rate, number of SNs and the number of counts of the most active SN.

RESULTS

Seventy-seven penile DSNB procedures in 75 patients (67 ± 11 years) were included. The detection rate of DSNB was 91% and 96% per procedure and groin, respectively. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were 79%, 100%, 97% and 100%, respectively. More SNs were seen on SPECT/CT than on static planar imaging (1.33 vs. 1.17, p = 0.001). The mean counts per SN on static planar imaging was lower compared to SPECT/CT (1343 vs. 5008; p < 0.0001). There was a positive correlation between the total counts of the SN on the static planar image and the SPECT/CT (r = 0.79, p < 0.0001). Only one out of seventy-five patients (1%) experienced DSNB-related adverse events. After 18 months, 58 patients remained disease free (77%), 13 developed local recurrence (17%), and 4 developed lymphatic or distant metastases (5%).

CONCLUSION

DNSB is a safe diagnostic procedure with a good detection rate and in particular high negative predictive value. It can therefore prevent overtreatment of patients with negative inguinal groins on clinical examination and DSNB examination. Finally, DSNB enables an early detection of occult metastases which would not be visualized with standardized imaging modalities.